Method of producwood



Oct. 21,. 1947. 2,429,272

M. MELAMID METHOD OF PRODUCING WOOD TAB AND CHARCOAL BY SUCCESSIVE DIRECT A IND EC EATING STEPS Filed e l l9 INVEN TOR. gar/zed wamd Md. 1. H @11 Patented Oct. 21, 1947 UNITED STATES TENT OFFICE Michael Melamid, New York, N. Y. Application June '15, 1943, Serial No. 490,922

ZCIaims. 1-

My invention relates to improvements in methods of producing wood tar, particularly to improvements in methods of producing wood tar'by means of kilns.

As it is well known inthe art, the principal methods used for the production of wood tar are the kiln method, the retort method and the tunnel method. Kiln tar has several important advantages over retort or tunnel tar, but its pro-- duction is substantially more expensive and cumbersome due to the lower yield per unit of wood, the methods and installations conventionally used for the formation of wood tar by means of kilns, the time necessary for operating a kiln, and the careful preparation andpiling of the Wood that are required for a production of tar with conventional methods and installations.

One object of my invention is a novel and improved method by which the yield per unit of wood is greatly increased.

Another object of my invention is a great increase of the yield per unit of wood without substantially afiecting the advantageous properties of kiln tar.

Another object of my invention is a novel and improved method by which the length of time required for the formation and discharge of tar is substantially reduced.

Another object of my invention is a novel and improved method by which a successful operation of a kiln is made possible without the expensive and time consuming preparation and piling of the wood to be used in the kiln which are indispensable with kilns to be operated according to conventional methods.

Another object of my invention is a novel and improved method by which the use of valuable, resinous tar-producing wood for generating the necessary heat in the kiln is greatly reduced or even practically eliminated and replaced by use of inexpensive, non resinous wood or wood otherwise not usable for tar production or by other inexpensive fuels.

Other and further objects and advantages of my invention will be more fully explained hereinafter.

It is obvious from the previous description that by my novel and improved methods and installations the costs of producing kiln tar are greatly reduced without losing the advantages of kiln tar over retort and tunnel tar.

In carrying out my invention, I first prepare a kiln by forming a pile from pieces of resinous wood, generally pine wood, preferably split stumps and trunks. This pile is covered. with a crete, preferably concrete containing asbestos fibers for confining the piled wood. The heat resisting cover may be made of any suitable material. I have obtained good results by using sheet metal leaving one or more vents near the top of the cover.

In kilns operated by conventional methods the trunks and stumps to be used are cut into comparatively small pieces and placed upright, slight- 1y slanted into the kiln to form a roughly frustroconical pile. The purpose of this arrangement is to leave as little air space as possible between the individual pieces of wood in order to obtain a smoldering or slow burning of the wood rather than a fast combustion while the extraction and formation of tar are in progress. It is obvious that such careful cutting and piling of the wood are rather tedious, time consuming and hence expensive. I can, of course, carry out the method according to my invention in connection with a conventionally charged kiln, but I have found that very good results can be obtained by simply charging the kiln with wood without carefully piling and placing the individual pieces of wood. Such simplified charge requires only a fraction of the time necessary for a conventional charge.

The charged kiln is ignited and operated in a conventional manner until the water content of the wood has been substantially evaporated by the generated heat and the interior of the kiln hasreached the temperature at which extraction, formation and discharge of tar begin. The necessary heat can be generated by covering the outside of the resinous wood pile in the kiln with less valuable wood such as kind-ling wood or by using other inexpensive fuel. This pro-heating period cannot be exactly defined by fixing the length of time or the temperature within the interior of the kiln since various factors such as size of the wood, wind, and outside temperature are influential. However, I have found that the temperature within the kiln will average about 200 C. when the extraction and discharge of tar begin. A man skilled in the art will not have difficulties in ascertaining the end of. the pre-heated period.

The'first step ofv the method according to my invention is now completed. However, I do not Wa t9 be limited to the exact moment at which 3 the wood is substantially dried and form-ation and discharge of tar begin, but the period immediately before and after this moment shall be included in the pare-heating period previously defined as the first step of the method according to my invention.

As soon as the first step is completed, I apply external heat to the outside of the kiln. This external heat is regulated and adjustable so that the temperature in the interior of the kiln is raised to a temperature which is the most f avorable for the formation and discharge of the tar and which may be described as conventional temperature. This temperature is afiected by various factors such as the specific properties of the used resinous wood. It is usually between 250 and 400 C. A man skilled in the art will have no difiiculties to determine the correct temperature in each case.

When the formation and discharge of the tar cease, the second step of the method according to my invention is completed. Of course, it should be understood that the discharge of tar does not cease abruptly but diminishes gradually. In practice, the second step is completed when the discharge of tar has become so small that a further operation of the kiln would not be economic.

The external heat can be produced by any suitable means. I found it very convenient and inexpensive to place wood on the outside of the kiln, and particularly upon its cover. This wood is then ignited and produces the required higher temperature within the kiln. It is preferable to cover the'outer wood with a second cover suitablyspaced from the inner cover so that the outer cover forms'a jacket. Instead of wood, any other suitable fuel such as inexpensive fuel oil can be used. It is also possible to guide hot gases through a jacket surrounding the kiln or its cover partly or completely.

As it is apparent from the previous description, the operation of a kiln according to my invention may be divided into a pre-heating period (first step) and an extraction and discharge period (second step). Only during the first step the entire heat is generated within the kiln. As previously explained, inferior fuel can be used for this purpose. During the second or main step the major portion of the heat'required for the formation and discharge of tar is furnished by external heat. Hence it is not necessary to burn and waste a substantial part of the resinous tarforming wood within the kiln in order to create the necessary heat as it is the case with conventional kilns. As a result the yield of tar per unit of wood is increased about 50%, thus approaching, reaching or even surpassing the average yield of retorts or tunnels per unit of wood. Furthermore, due to the use of external heat, the time conventionally required for the operation of a kiln is substantially reduced to wit, from about 14 to 21 days to about 4 to '7 days. This substantial saving of time of operation reduces the production costs of the tar considerably.

The method according to my invention can be described as a novel combination between the kiln method and the retort method, since the kiln is operated somewhat similar to a retort during the second step. Yet the produced tar retains all superior qualities of kiln tar such as a rather light color which is highly desirable for many purposes; it contains less phenols than retort or tunnel tar, it is heavier than retort tar and not deteriorated or discolored by contact with metal parts as is retort tar. Furthermore, the installation costs for carrying out the method according to my invention are not substantially higher than the costs for a conventional kiln and very much less than the installation costs for carrying out the retort or tunnel method.

I have found that the method according to my invention can be further improved by reducing the combustion taking place within the kiln at about the same time when the application of external heat begins at the end of the preheating period. This can be easily accomplished by reducing or limiting the admission of air into the kiln. The admission of air should be limited so far that the resinous, tar-forming wood within the kiln just continues to smolder. I hereby prevent a consumption and waste of tar forming wood thus further increasing the yield per unit of wood.

Under certain circumstances, it is advisable to discontinue the admission of fresh air into the kiln entirely.

According to an advantageous modification of the method according to my invention, I combine steps 1 and 2. I accomplish this by applying external heat from the beginning of the operation and by providing direct connections between the interior of the kiln and the external heat. The external heat will ignite the wood within the kiln which will smolder and burn slowly, thus contributing to the generation of heat within the kiln which is necessary for the formation and discharge of tar. The admission of fresh air into the interior of the kiln should be regulated so that the tar-forming wood within the kiln cannot burst into open flame. The application of external heat is continued until the discharge of tar practically ceases.

It will be easily understood from the previous explanation that the modified method according to my invention is based on the same principle as the first described method.

I have found that the quality of the produced tar can be improved by admitting steam into the interior of the kiln after the formation and discharge of tar have begun.

I have further found that valuable products can be obtained from a kiln by withdrawing the gases formed in the kiln while the extraction and formation of tar are in progress. These gases contain various light hydrocarbons, methanol, light pine oils and turpentine which can be easily recovered.

In order to improve the quantity and quality of the charcoal obtained in the kiln as a byproduct of the tar production, I discontinue the application of external heat and increase the admission of fresh air into the kiln after the formation and discharge of tar have been practically completed. This will result in a livelier burning of the wood within the kiln which will drive out the rest of the resin remaining in the wood and complete the carbonization of the wood. I have found that by this third step the porosity and other desired properties of the produced charcoal are greatly improved. The length of time which is required for carrying out the third step of the method according to my invention cannot be accurately defined since several variable factors such as quantity and kind of wood will influence the required length of time. However a man skilled in the art will have no difiiculties to determine the completion of the production of charcoal in each individual case. Under certain circumstances it is advantageous to continue the carbonization of the wood until the wood is transformed into soot-black.

The methods according to my invention can be carried out in various installations.

The accompanying drawing shows diagrammatg ically the basic features of kilns suitable for carrying out the methods according to my invention.

Figure 1 is a sectional view of a diagrammatic illustration of a kiln according to my invention.

Figure 2 shows a sectional view of a modification of a kiln according to my invention.

Figure 3 is a plan view of a modification of a detail of a kiln according to my invention, and

Figure l shows a detail of Fig. 3 on an enlarged scale.

The same numerals in the various figures designate the same parts.

The kiln shown in the figures comprises atank I which may be constructed of brick, concrete mixed with asbestos fibers or any other suitable heat-resisting material. The kiln may be built partly below the surface of the ground in order to facilitate the servicing of the kiln during the operation. It may have any suitable cross-section, such as circular, square or rectangular. The kiln is charged with cut, resinous tar-forming wood until a flat cone is formed extending over and above the upper edge of tank I of the kiln. After the kiln has been charged it is covered with a cover 2 which may consist of any suitable material, for example, sheet metal. The cover is preferably made of several detachable sections to facilitate the handling of the cover. The cover should be as close as possible to the wood in order to reduce the air space in the kiln. Fresh air is admitted into the kiln by means of one ormore openings 3. In order to create the necessary draft, one or more openings 4 are provided in cover 2. Steam may be admitted into the kiln by means of one or more pipes 5'. Valuable gases' gathering in the upper part of the kiln can be withdrawn through one or more pipes 6.

The external heat to be applied during the second step of the method, according to my invention is generated between a jacket formed by inner cover '2 and an outer conical cover I. This outer cover may also consist of sheet metal or any other suitable heat-resisting material and is preferably made of several detachable sections in order to facilitate its handling. Outer cover I may rest on a ring 8 to which it is fastened by any suitable means. Ring 8 and outer cover I may bemade of one piece. It is also possible to secure ring 8 to cover 2. Ring 8 serves to space outer cover 1 from inner cover 2. However, it is understood that any other means can be used to space cover I from cover 2. Fresh air is admitted into the space between covers 2 and I by one or more openings 9. Opening II] at the top of cover I or at any other suitable place secures the necessary draft. At the outside of cover 2 one or more, preferably perforated grates I I and I2 are provided on which wood or other fuel used for producing the required external heat is placed. If the kiln is taken in operation, the wood in the interior of the kiln is ignited and kept burning until the wood in the kiln is substantially dried out and the temperature within the kiln has reached approximately the point at which the formation and discharge of tar begin. Then the wood or other fuel placed in the space between covers 2 and l is ignited. The external heat hereby created raises the temperature within the kiln to the point which is required for an economic formation and discharge of tar. The

6. admission of air'through openings 3 maybe now reduced by partly closing these openings. The tar is discharged. through channels 27 in the bottom of th'e' tank.

If desired, steam can be admitted through pipes 5.

soon .asthe formation and discharge of tar are practically completed, the generation of eX- ternal heat is discontinued. This can be conveniently accomplished by ceasing to feed fuel into the space between covers 2 and I. simul taneously the admission of fresh air through openings 3 may be again increased until thefpro duction of charcoal within the kiln is completed. Then the tip of the kiln is dismantled and: the produced charcoal may be removed.

In the embodiment shown in Figure 2 conical cover 2 is replaced by a fiat cover I3. This cover may be corrugated in order to increase the ex-' change of heat. Cover I3 is slidably fitted into tank I of the kiln. It is preferably provided with a ring M to facilitate a sliding movement.

Tank l is filled with cut resinous tar-forming wood, then tightly covered with fiat cover I3. The cover is preferably weighed down by Weights I5, for example stones.

The external heat to be applied during the second step of the method according to my invention is generated between cover I3 and an outer conical cover I6. The external heat may be produced by placing wood or other fuel oncover is and igniting it at the end of the preheating period. New fuel may be added by suit-- able openings in cover I5. This cover is further provided with one or more openings IT and I8 for the admission and discharge of air and combu-stion gases respectively.

Due to the slideab'le arrangement of cover I-3 it will sink gradually when the volume of the wood in the kiln decreases during the burning. This has the advantage that the air space in the kiln is always kept at a minimum whereby the desired slow burning or smoldering of the wood during the formation and discharge of tar are secured.

The operation of a kiln according to Figure 2 is similar to the operation of a kiln according to Figure 1, so that no further detailed description is deemed necessary.

Figure 3 shows a plan view of a conical cover which may be used as inner or outer cover. It comprises a number of sections I9 which overlap each other. The width of the individual sections is indicated by brackets 20. The outer ends of adjacent sections are pivotally connected by bolts 24 fastened to one of two adjacent sections. The sections do not extend to the center of the cone formed by the cover but leave a central circular space 23.

The cover formed by sections I9 is supported in the illustrated or open position by the wood on which it is placed. As soon as the wood which may be the wood in tank I or Wood placed on the inner cover is beginning to sag during the operation of the kiln, the individual sections of the cover follow this movement by pivoting about their pivotal connections formed by bolts 2| and slots 22. The free ends of section I9 move closer together and the free central circular area 23 is gradually diminished as indicated by the smaller dotted circle 24. The purpose of this arrangement is the same as the purpose of the slideable cover I3, to wit-to keep the free air space within the kiln or between the outer and inner cover if the cover according to Figure 3 is used as outer cover at a minimum. The downward movement of the sections of the cover can be assisted by placing weights on the cover. If the cover is used as inner cover, these weights comprise preferably blocks 25 made of suitable-heat resisting material which are held together by wires or chains 26. The structure thus formed can serve as grates on which the wood or other fuel used for producing the external heat are placed.

If kilns as shown in Figures 1 and 2 are used to carry out the modification of my invention in which method steps 1 and 2 are combined, openings must be provided in the inner cover permitting an ignition of the wood within the kiln by the external heat.

The specific illustrations shown and described have been given by way of illustration and not by way of limitation. The illustrated structures are subject to wide variations and modifications without departing from the scope or intent of the invention.

Having thus described my invention, what I desire to protect by Letters Patent is:

1. Method of producing wood tar and charcoal in kilns of the class described which consists in that first heat is generated in the interior of the kiln by partially burning the wood within the kiln for. raising the temperature within the kiln to approximately the point at which formation and discharge of tar begin, that then heat generated by an external source of heat is applied to the kiln for raising the temperature within the kiln to the temperature conventionally used for the formation and discharge of tar and maintaining the temperature at this point during the formation and discharge of tar, that the generation of heat by burning of wood in the interior of the kiln is limited during the formation and discharge of tar and that after the termination of the formation and discharge of tar the application of extemal heat is discontinued and the generation of heat in the interior of the kiln by burning of wood is again increased until the production of charcoal is completed.

2. Method of producing wood tar and charcoal in a kiln of the class described which consists in that the wood with which the kiln is charged is ignited for raising the temperature within the kiln to approximately the point at which formation and discharge of tar begin, that then wood partly surrounding the kiln is ignited for raising the temperature within the kiln by the external heat generated by the said surrounding wood to the temperature required for the formation and discharge of tar and maintaining the temperature at this point during the formation and discharge of tar while at the same time reducin the generation of heat within the kiln by reducing the admission of air into the kiln, and that, after completion of the formation and discharge of tar, the generation of external heat is discontinued and the admission of air into the kiln is increased for raising the temperature within the kiln by partially burning of the kiln charge until the production of charcoal is completed.

' MICHAEL MELAMID.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,757,144 Schaffer May 6, 1930 129,815 Goodrich July 23, 1872 1,227,148 Iwamoto May 22, 1917 FOREIGN PATENTS Number Country Date 154,272 Austria Sept. 10, 1938 693,982 Germany a July 23, 1940 131,006 Great Britain Aug. 18, 1919 

